The present invention relates to a vehicle tire having improved sipes capable of improving the rigidity of tread rubber.
In order to improve running performance on snowy and icy roads, cuts or narrow slits so called sipes are formed in the tread portion. Such sipes provide edged corners in the tread face and thus grip performance is improved correspondingly. Accordingly, as the number of the sipes increases, the performance on snowy and icy roads may be improved, but the rigidity of the tread portion inevitably decreases. Therefore, if the number or density of the sipes is increased beyond some value, the performance lowers by contraries. Thus, it is difficult to improve on-the-snow-and-ice performances by increasing the number of the sipes.
It is therefore an object of the present invention to provide a vehicle tire in which on-the-snow-and-ice performances are improved by increasing the number of sipes without suffering from a decrease in the tread rigidity.
According to the present invention, a vehicle tire comprises a tread portion and sipes disposed therein,
each of the sipes comprising an radially outer part and radially inner parts,
the radially outer part, extending radially inwards from the tread face to a certain depth H, and extending continuously in the longitudinal direction of the sipe,
the radially inner parts extending radially inwards from the radially inner end of the radially outer part at the above-mentioned depth H,
the radially inner parts comprising at least one first inner part inclined towards one side of the radially outer part and at least two second inner parts inclined towards the other side of the radially outer part,
the first and second inner parts alternating with each other in the longitudinal direction of the sipe.